The Solid State and Structural Chemistry Unithttp://sscu.iisc.ernet.in
SSCUMon, 19 Nov 2018 04:47:52 +0000enhourly1https://wordpress.org/?v=4.9.825th OCT- Today 4.00 PM SEMINAR Speaker: Mr. Sambunath Das Title Eigenstate Thermalization Hypothesis Date & Time: Thursday 25th October, 2018 at 4.00 PM Venuehttp://sscu.iisc.ernet.in/seminar-and-lecture/today-4-00-pm-seminar-speaker-mr-sambunath-das-title-eigenstate-thermalization-hypothesis-date-time-thursday-25th-october-2018-at-4-00-pm-venue/
Thu, 25 Oct 2018 04:08:53 +0000http://sscu.iisc.ac.in/?p=1670Dear All,
SOLID STATE & STRUCTURAL CHEMISTRY UNIT
INDIAN INSTITUTE OF SCIENCE
BANGALORE – 560 012
SEMINAR
Speaker: Mr. Sambunath Das
Title
Eigenstate Thermalization Hypothesis
Date & Time: Thursday 25th October, 2018 at 4.00 PM
Venue: SSCU AUDITORIUM
Abstract:
Thermalization in an isolated classical system can be explained through chaotic dynamics and ergodicity. Can we use the same principle to explain the thermalization in quantum mechanical isolated system? Accorrding to J.M. Deutsch and M. Srednicki, this question can be answered through Eigenstate Theremalization Hypothesis (ETH). The ETH states that for non-integrable systems, the expectation value of any local observable for each energy eigenstate is same as the average value of that observable in the microcanonical ensemble. In my talk, I will discuss in detail quantum thermalization through ETH and also show how it is different from the classical thermalization. I will give a numerical example of ETH and show where ETH fails in different systems.
References:
1. Mark Srednicki ,Chaos and quantum thermalization,Phys. Rev. E, 50(2), 888-901,1994.
2. Marcos Rigol, Vanja Dunjko and Maxim Olshanii,Thermalization and its mechanism for generic isolated quantum systems,Nature Letter, 452, 854-855, 2008.
3. Hyungwon Kim, Tatsuhiko N. Ikeda and David A. Huse,Testing whether all eigenstates obey the Eigenstate Tharmalization Hypothesis, Phys. Rev. E, 90, 052105, 2014.

Self-replication is an irreversible process carried out by living species through which, one produces copies of itself. Based on intuition, one can explain this as entropy driven process. In order to understand the thermodynamics of it, one must know the relation among heat production, growth rate, internal entropy and sustainability of the replicator.
In this talk I will formulate a general entropy change relation for irreversible processes. I will use the relation to explain the thermodynamic picture of various self-replicating systems like, exponentially growing cells, growth rate of polynucleotides & bacterial cell division.
Apart from entropy driven processes, I will use the aforementioned relation to explain self-assembly.

SPECIAL SEMINAR
by
Dr. Atanu Kumar Metya
Department of Chemical Engineering
Indian Institute of Technology Kanpur

Title

Molecular Simulation Study of Ice Nucleation in the Presence of Foreign Substances

Date & Time : Wednesday 3rd October 2018 at 3:00 PM
Venue : SSCU Auditorium
Abstract:
Ice formation from liquid water is one of the most common phase transitions on Earth, affecting everything from the global climate in the Earth’s atmosphere to cryopreservation of cells and tissues. Nucleation can either occur homogeneously or heterogeneously. In nature and industry, freezing almost generally induces by the presence of foreign seed (i.e., heterogeneous ice nucleation). Despite a large amount of experimental and theoretical studies on heterogeneous nucleation, still many aspects of the freezing process remain unsolved. For example, how do different wetting states on nanostructured surfaces affect the ice nucleation rate? What is the surface structure of ice near a solid surface in the presence of impurities? In experiments, accurate capture of nucleation events as well as quantification of the freezing process is difficult due to practical challenges in designing relevant experiments. However, in this direction, molecular simulations play an important role in the study of nucleation processes. This talk will present research work in the broad area of heterogeneous crystallization of supercooled pure water and solutions on the substrates using molecular dynamics simulation. First, I investigated the nucleation behavior of a supercooled water droplet on the textured surfaces. The simulation results show that the nucleation rate depends on the surface fraction of a substrate as well as the wetting states of the water droplets. Next, I studied the heterogeneous crystallization of supercooled water in the presence of nanoparticle (NP) and salt. At lower NP–water interactions, the nucleation rate is indifferent, while higher at NP–water interactions, the nucleation rate is found to reduce with the addition of nanoparticles. Furthermore, I worked on the structure and freezing temperature of binary water−salt solution on hydrophobicity/hydrophilicity of surfaces. Here we investigate the effects of salt concentrations and the solutesubstrate interaction strengths on nucleation behavior of the aqueous solutions. Finally, I studied the ice adhesion mechanism on lubricantimpregnated surfaces (LISs) using steered molecular dynamics simulations. We found that the adhesion strength of ice on nanotextured surfaces impregnated with lubricant films to be higher compared to that on textured surfaces in presence excess lubricant films and the ice adhesion strength depends on the texture density. This systematic study enhances our understanding of ice adhesion mechanism on LISs and the effect of texture density on the adhesion properties, which can be applied for designing novel anti-icing surfaces with extremely weak ice adhesion strength.

ALL ARE CORDIALLY INVITED TO ATTEND

Chairman, SSCU

Coffee/Tea : 2.30-2.45 PM

]]>27th September, 2018 at 4.00 PM-SEMINAR Speaker: Ms. Arpita Mukherjee Title Slow Lighthttp://sscu.iisc.ernet.in/seminar-and-lecture/27th-september-2018-at-4-00-pm-seminar-speaker-ms-arpita-mukherjee-title-slow-light/
Thu, 27 Sep 2018 04:44:17 +0000http://sscu.iisc.ac.in/?p=1659Dear All,
SOLID STATE & STRUCTURAL CHEMISTRY UNIT
INDIAN INSTITUTE OF SCIENCE
BANGALORE – 560 012
SEMINAR
Speaker: Ms. Arpita Mukherjee
Title
Slow Light
Date & Time: Thursday 27th September, 2018 at 4.00 PM
Venue: SSCU AUDITORIUM
Abstract:
Around 1864 James Clerk Maxwell determined the velocity of light in vacuum considering that light is an electromagnetic wave. Later on Albert Einstein proposed from the theory of relativity that light speed is a universal constant in vacuum. However, when light enters a medium the velocity of light decreases due to light-matter interaction. The refractive index of the medium governs the velocity of light propagating inside the medium. Generally for a pulse of light propagating inside a medium, the phase velocity depends only on the refractive index of the medium, while the group velocity also depends on the variation of refractive index with frequency. In 1999, Danish Physicist Lene Hau showed that the group velocity of light can be slowed in certain media to a speed as slow as that of a good bicycle (17m/sec), or even slower. This seminar will describe methods used to slow down the speed of light to this extremely slow regime.
References:
[1] Ketterle et al. Phys. Rev. Lett. 3969, 75, 1995
[2] Harris et al. Phys. Rev. Lett. 2593, 66, 1991
[3] Hau et al. Nature 594, 397, 1999
[4] Cornell et al. Nature 198, 269, 1995
[5] Mark Fox, Quantum optics An Introduction, Oxford university press, 2009
[6] Hau et al. Nature 490, 409, 2001

The second half of 20th century could be called the microelectronic era with sufficient justification. Spintronics is a new class of devices which gave a huge breakthrough in the microelectronic world. Spintronics is primarily based on spin degrees of freedom in addition to charge degrees of freedom of an electron. Electrons have both charge and spin, but until recently, charges and spins have been considered separately. In conventional electronics charges are manipulated by an external electric field but spins are ignored. The spin based electronics are more powerful for certain types of computations as compared to that of conventional electronic devices. Further, its smaller size and relatively less consumption of electricity makes it advantageous over other charge based electronic devices .

In this presentation I shall be discussing the fundamental concepts of spintronics and the advantages of molecular spintronics over the inorganic spintronics. I shall present the case study of LSMO/Alq3/Co [2,3] interfaces which shows high Magnetoresistance (~200%), behaving as an “organic spin valve”.

Surface plasmon polaritons are spatially confined electromagnetic field modes at a metal-dielectric interface generating ultrashort and intense optical fields, which can potentially be used to enhance the optical response of quantum emitters. Consequently, the optical responses of hybrid nanostructures comprising active materials, e.g., semiconductors or layers and metals is currently attracting considerable attention. In this talk, some aspects of the fundamental physical mechanism in active plasmonics, namely the SPP-quantum emitter dipole coupling probed using various spectroscopy techniques will be explored.

Piezoelectric materials are a class of materials which generate electrical potential in response to applied stress. This coupling of electrical and mechanical properties is used for various electromechanical applications. A lot of research has been going on in the field of piezo ceramic materials with an objective to enhance the piezoelectricity.

In this presentation I shall discuss how the concept of Morphotropic Phase Boundary (MPB) i.e., composition induced phase boundary in solid solutions, has been a tool not only to enhance the piezoelectric coefficient of the material but also to design a series of materials having improved electromechanical properties. I shall explain with examples of Pb-free and Pb-containing piezo ceramic systems and how the introduction of a small amount of structural heterogeneity near MPB compositions has a tremendous effect in increasing the electromechanical properties.

Date & Time : Monday 27th August, 2018 at 4:00 PM
Venue : SSCU Auditorium
Abstract:
Quantum materials are systems whose properties are governed by quantum behavior and provide a common thread linking frontiers of physics, chemistry, materials science and engineering. In this talk, I will give two examples from our recent work demonstrating intriguing properties of such systems. In the first part, I will focus on emerging three-dimensional topological Dirac materials and describe strategies to engineer the creation, motion and annihilation of Dirac points using alloying [1] and light [2].

In the second part of the talk, I will present a special kind of phase transition that can occur at low temperatures by tuning a non-thermal control parameter and is the driver for exotic quantum phenomena that extend to elevated temperatures. I will present the concept of multiferroic quantum criticality — in which both magnetic and ferroelectric quantum phase transitions occur in the same system — that we have recently introduced [3]. I will describe the associated experimental signatures and material systems to realize it, and highlight possible future directions.
References:
[1] A. Narayan, D. Di Sante, S. Picozzi, and S. Sanvito, Phys. Rev. Lett. 113, 256403 (2014).
[2] A. Narayan, Phys. Rev. B 91, 205445 (2015).
[3] A. Narayan, A. V. Balatsky, and N. A. Spaldin, arXiv:1711.07989 (under review).